1. Technical Field
The present invention relates to a fixing device capable of sensing a surface temperature of a heating roller, and an image forming apparatus including the fixing device.
2. Description of Related Art
In an image forming apparatus such as a copying machine and a printer device, a fixing device of a heating type is widely used to fix onto recording paper a toner image transferred to the recording paper. The fixing device of the heating type includes a heating roller having a heating unit such as a heater, and a pressurizing roller press-fitted to the heating roller, wherein recording paper having a toner image transferred thereon is passed through while sandwiched between the heating roller and the pressurizing roller, a toner on the recording paper is melted, and the toner image is fixed onto the recording paper by being further pressurized.
In such a fixing device, in order to surely melt the toner on the recording paper and prevent the recording paper from being adversely affected, a surface temperature of the heating roller needs to be accurately controlled. Therefore, conventionally, a plurality of thermistors are pressed against the surface of the heating roller, and temperatures of a center and an end of the surface of the heating roller are sensed to control power supply to a heater. Whereby, the surface temperature of an entire body of the heating roller is controlled to be uniformly maintained.